单选题
The{{U}} {{U}} 66 {{/U}} {{/U}}is a general
description of the architecture of a workflow management system used by the
WFMC, in which the main components and the associated interfaces are summarized.
The workflow enactment service is the heart of a workflow system which consists
of several{{U}} {{U}} 67 {{/U}} {{/U}}. In a workflow system, a
process is specified using the process definition tool. Usually, processes are
defined in terms of a{{U}} {{U}} 68 {{/U}} {{/U}}, which
consists of{{U}} {{U}} 69 {{/U}} {{/U}}indicated using a circle,
and{{U}} {{U}} 70 {{/U}} {{/U}}shown as a rectangle. These two
components can be linked by means of a directed arc.